The present invention relates to a vehicular headlamp having a tilt measuring device for checking whether or not the aiming direction of a light beam from the vehicular headlamp, i.e., the beam angle of the headlamp, is correct, and if it is not correct, allowing the beam angle of the headlamp to be corrected in a simple manner.
In the description to follow, a headlamp of the reflector-movable type will be described in which the reflector is tiltably mounted within the lamp body. As shown in FIG. 27, the rear side of a reflector 202 is supported by a lamp body 201 at three points, namely, by two longitudinally extending aiming screws 203 and 204, and a pivot point 205. In FIG. 27 showing a plan view of the reflector, the two aiming screws 203 and 204 extend vertical to the surface of the paper. The two aiming screws 203 and 204 are rotatably supported on the rear side of the lamp body 201. The support points of the reflector 202 (nut members of the reflector forming aiming screw support members) are disposed orthogonal to each other with respect to the pivot point 205 when seen from the front of the lamp. By turning the two aiming screws 203 and 204, the reflector nut members threadedly joined to the two aiming screws 203 and 204 move back and forth along the two aiming screws 203 and 204, so that the reflector 202 turns about the horizontal axis Lx and the vertical axis Ly, thereby horizontally and vertically adjusting the angle of the output light beam of the lamp. Reference numeral 206 designates a bulb mounted on the reflector 202.
Published Unexamined Japanese Patent Application No. Hei. 5-290604 discloses a first conventional tilt measuring device. As shown in FIGS. 28 and 29, the measuring device is formed of a guide mhember 212, a-nut member 214, a zero-adjust plate 218, a cursor 218a formed on the zero-adjust plate 218, and a scale 212a formed on the guide member 212. The guide member 212 is fastened to the rear wall of the lamp body 201 and extends in parallel with the aiming screw 203. The nut member 214 opens at one side to be shaped like a "U" in cross section. The zero-adjust plate 218 is mounted on the nut member 214, and engages the guide member 212 so as to be slidable along the guide member 212.
The cursor 218a slides along the scale 212a when the aiming screw 203 is turned. When the reflector 202 has been positioned by a tilt adjustment (aiming adjustment) so as to render the beam angle of the headlamp proper, and the cursor 218a is set at the zero point on the scale 212a. (This operation will be referred to as a zero-point adjustment).
If later the tilt position of the reflector is somehow disturbed and the beam angle of the headlamp deviates from the correct angle, the cursor 218a will deviate from the zero point on the cursor 218a by a distance corresponding to the amount of deviation of the beam angle of the headlamp. With this construction, any person, skilled or unskilled, can easily carry out the aiming adjustment by merely turning the aiming screw 203 so as to remove the deviation of the cursor from the zero point on the scale (that is, to return the cursor 218a to the zero point on the scale 212a).
Published Unexamined Japanese Patent Application No. Hei. 4-198830 shows a second conventional tilt measuring device. As shown in FIGS. 30 to 33, the tilt measuring device is formed with a transparent case 220, a base member 222, a slide member 224, a coupling member 226, a reference line 221, and a scale 225. The transparent case 220 is mounted on a lamp body 201, enclosing an aiming screw 203. The base member 222, cylindrical in shape, is disposed within the transparent case 220 in a state such that it is rotatable with respect to the aiming screw 203. The slide member 224 is threadedly joined to a male threaded part 222a on the outer surface of the base member 222, and coupled with the transparent case 220 in a nonrotative fashion. The coupling member 226 is disposed between the base member 222 and the aiming screw 203, thereby coupling these components together. The reference line 221 is drawn on the transparent case 220. The scale 225 is formed on the slide member 224. With the structure of the tilt measuring device, the slide member 224 slides back and forth within the transparent case 220 when the aiming screw 203 is turned. The amount of deviation of the beam angle of the headlamp is indicated in the form of a corresponding amount of deviation of the reference line 221 from the zero point 225a on the scale. In FIG. 31, reference numeral 208 designates a screw support member of the reflector, which is threadedly joined with an aiming screw 204.
The tilt measuring device may take one of two states optionally, as shown in FIGS. 32 and 33. In a first state, the base member 222 is coupled with the aiming screw 203 (FIG. 33). The tips 227 of a pair of flexible pieces of the coupling member 226 are inserted into the concavities 223 of the base member 222, thereby to hold a rearward extending part 204 of the aiming screw 203 with the tips 227 (FIG. 33). The rear extended part 204 is rectangular in cross section. In a second state, the coupling member 226 is pulled out rearward (FIG. 32). Then, the tips 227 of the flexible pieces disengage from the concavities 223 of the base member 222, thereby to release the rearward extending part 204 of the aiming screw from being held (to disengage the base member 222 from the aiming screw 203). In this state, the aiming screw 203 may be turned independently of the base member 222.
In this second conventional device, in a state where the zero-point adjustment has been completed, the coupling member 226 is pulled out of the concavities 223 and the base member 222 is disengaged from the aiming screw 203. When an aiming adjustment is subsequently carried out, the reference line 221 remains placed exactly above the zero point 225a. Accordingly, there is no need of zero-point adjustment after the aiming adjustment.
The first conventional device is advantageous in that its construction is simple, but is disadvantageous in that the zero-point adjustment work is troublesome. That is, the zero-point adjustment is carried out in a complicated manner whereby a fixing screw 218b of the zero-adjust plate 218 is loosened, the zero-adjust plate 218 is slid with respect to the nut member 214, the zero-adjust plate 218 is properly positioned, and then the fixing screw 218b is tightened again.
In the second conventional device, when the coupling member 226 is pulled out to disengage the base member 222 from the aiming screw 203, and then the aiming adjustment is carried out, the reference line 221 remains placed just above the zero point 225a. Accordingly, no zero-point adjustment must follow the aiming adjustment.
In this respect, the second conventional device is very advantageous. However, the second conventional device is disadvantageous in that the number of parts required is large, which makes the structure of the resultant tilt measuring device complicated, and the assembly of the device to the headlamp is made correspondingly complicated.